The isolation of substantially pure 5-methylimidazo[4,5-e]-1,2-thiazin-4(5H)-one from the New Guinea sponge Neamphius huxleyi is reported in DeSilva, P. E., et al, J. Tetrahedron Lett. 32, 2707 (1991) and is the subject of U.S. Ser. No. 07/683,457. It has the structure ##STR1## which also may be depicted as ##STR2## It has been denoted neamphine.
Because screening testing of neamphine has indicated the potential for in vivo antineoplastic activity, synthesis thereof is desirable to increase the limited supply thereof available from the natural source to allow further definition of the biological activity and, in the event of determination of outstanding safety and efficacy, to provide a sufficient supply to satisfy demand.